1. Field of the Invention
The present invention relates generally to ink cartridges and ink supply systems. In particular, the present invention is directed toward ink cartridges and ink supply systems in which a pump is used to cause ink flow.
2. Description of Related Art
A known inkjet printer has a print head configured to selectively eject ink from nozzles formed in the print head toward a sheet of paper to form an image on the sheet.
This known inkjet printer uses a replaceable ink cartridge having an ink tank configured to store ink therein, and ink is supplied from the ink tank to the print head via an ink path formed between the ink tank and the print head.
The ink cartridge has an ink supply opening for supplying ink from the interior of the ink tank to the exterior of the ink tank. The ink supply opening is sealed with a sealing member, such as rubber. When the ink cartridge is inserted into a mounting portion of the inkjet printer, an ink needle positioned at the mounting portion penetrates through the sealing member, and ink stored in the ink tank is supplied to the ink path via the ink needle.
When the ink cartridge is replaced with a new ink cartridge, air bubbles may enter the ink tank and the ink path. Moreover, when the ambient temperature varies, air dissolved in ink stored in the ink tank may transform into air bubbles. If such air bubbles enter the print head, the print head may fail to eject ink. Another known inkjet printer, such as the inkjet printer described in JP-A-2000-85141, has an ink supply system in which a sub ink tank, which is connected to a print head, and a main ink tank are in fluid communication with each other via an ink path, and a pump, which is configured to deliver ink in opposite directions, is provided in the ink path. The pump is driven for returning ink in the sub ink tank to the main ink tank, and for supplying ink in the main ink tank to the sub ink tank. This system allows air bubbles to be separated from ink in the main ink tank, and then ink without air bubbles is supplied to the sub ink tank.
When the ink cartridge is manufactured, minute impurities, such as dust, may enter the ink tank. When the impurities contained in ink reach the print head, the impurities may clog the nozzles and the print head may fail to eject ink. Impurities, such as dust, may be more difficult to remove from ink than air bubbles because some of impurities float on ink, some impurities settle at the bottom of the ink, and other impurities suspend in ink. In recent yeas, because consumer demands for higher resolution of printed images has risen, the diameter of nozzles has decreased. Consequently, the desirability to remove impurities of sizes which previously could be ignored is increasing.